Strainer for pulp digesters



NOV. 24, 1936. H W GUETTLER 'El- AL 2,062,127

STRAINER FOR PULP DIGESTERS Filed Feb. 12, 1936 5 4She@13S-Sheet. l

H. w. GUETTLER ET AL STRAINER FOR PULP DIGESTERS Nov. 24, 1936.

5 Sheets-Sheet 2 Filed Feb. 12, 1936- mw. ww 1 NOV- 24, 1936 H. w. GUETTLER ET Al. 2,062,127

STRAINER FOR PULP DIGESTERS v Filed Feb. 12,y 1956 5 sheets-sheet s Nov. 24, 1936. H. w. GUETTLER Er AL 2052J27, Y

STRAINER FOR PULP DIVGESTERS,

' Filed Feb. 172,v 1936 5 Sheets-Sheet 4 Yara/20c r Gn/2.32%@ fase@ NOV 24, 1936- H. w. GUETTLER ET AL. 2,062,127

STRAINER FOR PULP DIGESTERS v5 sheets-sheet 5 Filed Feb. l2, 1936 Patented Nov. 24, 1936 PATENT VOF.`ICEI STRAINER FOR PULP DIGESTERS Herbert W. Guettlen Glencoe, and Clarence J. Christiansen, Evanston, Ill., assignors to Fibre Making Processes, Inc., Chicago, Ill., a corporation of Illinois vvAppli-mation February 12, 1936, serial No. 63,494

11 Claims.

This invention relates, to pulp digesters such as used in the paper making industry, and has to do with the strainer and associated parts of a digester.

It is common practice in operating digesters` to circulate the liquor by drawing a part thereof from the digester and returning the liquor thereto, by means of a suitable pump. It is necessary to provide a strainer to prevent withdrawal of the chips and bres from the dlgester. 'Ihe strainery may be located at the top or bottom, or any suitable intermediate position within the digester, This strainer-is subjected to high pressures and severe stresses withinthe digester and must be of adequate mechanical strength and supported in such manner as to eliminate possibility `of warping or breaking of the strainer with possible serious results due to the strainer, or parts thereof, becoming detached and dropping into the digester. 'I'he strainer must also be of adequate capacity and great care y is necessary in connecting this strainer to the conduit for withdrawing the liquor, particularly `in digesters employing acid liquor. Such digesters are constructed with an outer shell of ordinary steel, which is readily attacked by the acid, and an inner. acid resistant lining. If leakage of acid to the outer shell occurs, with consequent weakening of the latter, serious danger to the operators accrues due to the fact that the digester is operated under relatively high pressure.

In general, our invention is directed to the strainer and associated means such that adequate mechanical strength is provided for, ample capacity of the strainer Ais assured, and possibility of access of the acid liquor to metal parts readily attacked by the acid is eliminated. Another object of our invention is to provide a strainer and associated supporting means therefor so constructed and arranged that objectionable stresses, due to expansion and contraction of parts, are prevented and ready removal of the contents of the digester, when discharging the same, is not interfered with. A further object is to provide an outlet connection which may be assembled with expedition and facility, and associated means for assuring a seal about certain portions of such connection eiective to prevent access of the acid liquor to metal parts susceptible to attack by the acid. Another object is to provide a strainer and associated convantages will appear from the detail description.

In the drawingsz- Figure 1 is a transverse sectional view through a. digester with a strainer and associated part embodying our invention applied thereto;

Figure 2 is ay fragmentary vertical sectional view taken substantially on line 2-2 of Figure 1, on an enlarged scale, certain parts being shown in section;

Figure 3 is a fragmentary vertical sectional view taken substantially on line 3`3 of Figure 1, on an enlarged scale;

Figure 4 is 'a fragmentary vertical sectional viewltaken substantially on line 4-4 of Figure 15 Figure 7 is a detail perspective view of the 25 means for supporting and closing one end of the strainer;

Figure 8 is a View in elevation, partly broken i away and in section, of a pulp digester for using alkali liquor, showing a strainer and associated supporting and connection means embodying our invention appliedv thereto;

Figure 9 is a sectional View taken substantially on line 9-9 of Figure 8, on an enlarged scale;

Figure 10 is a fragmentary vertical sectional View taken substantially on line Ill-I0 of Figure 9, on an enlarged scale, broken away and shown in section;

Figure 11 is a fragmentary vertical sectional view taken substantiallyon line Il-II of Figure 9, onfan enlarged scale, partly broken'away; and p z l Figure 12 is a fragmentaryfvertical sectional view taken substantially on line |2-I2 of Figure 8,-certairi parts being shown in elevation and the major portion of the d igester being broken away. f

In Figures -1 to 7, inclusive, we have shown our invention as applied to a digester used in what i's known as the sulphite process, 'the liquor employed being a solution of sulphurous acid.V The digester is, in general, of known construction and comprises an outer shell a of ordinary steel and an inner lining b resistant to the acid liquor used in the digesting process. A charging neck c is provided at the top of the digester and is nor, mally closed by a removable cover d, as shown in Figure 8. A discharging neck e is provided at the bottom of the digester and has bolted thereto a fitting f in the form of an elbow from which extends a discharge pipe g controlled by a valve h. A pipe i extends from elbow f for connection to circulating means (not shown) effective for withdrawing liquor from the digester and returning it to the bottom or lower portion thereof. We also preferably provide a pipe Ic to which a portion of the withdrawn liquor is supplied from the circulating means, this pipe being connected to a spray device (not shown) within the digester, adjacent the top thereof, for spraying liquor onto chips which may be exposed above the liquor, thus maintaining the chips moist andpreventing objectionable charring thereof. Preferably, we employ a liquor circulating and heating and spraying system which is similar, in general, to that disclosed rin United States Patent No. 1,942,685, issued January 9, 1934, to Andreas Christensen, for Sulphite pulp dlgester system, though our invention is not limited to the use of this particular system and any other suitable or preferred means for circulating the liquor, either with or without associated spraying means, may be employed.

The strainer I5 of our invention comprises a plurality of Sections I6 and I6a disposed in endwise alignment and opening one into the other. Each of these sections is of arcuate shape in plan and the strainer is disposed in close proximity to the inner face of liner b, conforms in curvature to the curvature of the digester and, in the illustrated embodiment, extends the semi-circumference thereof. It will be understood, however, that the extent lof'the strainer may bevaried to suit conditions, and it may extend throughout the en- `tire interliorA circumference of the digester or for a portion only thereof, whether more or less than half of the interior circumference of the digester, as required.

Each strainer section I6, as well as section |6a, is of triangular cross section, comprising an imperforate back wall I1 and perforated upper and lower front walls |8 and I9, respectively, preferably braced by reinforcing ribs 20 disposed within the strainer section and at the outer faces of. these walls. It will be noted that the wall I8 is fiat and inclined downward and inward of the digester, wall I9 being flat and inclined downward and outward of the digester. Disposing the walls I8 and I9 in this manner assures that any material which may tend to settle upon wall I8 will be discharged therefrom downwardly into the digester, and that no material can settle upon wall I9. In this manner we effectively eliminate possibility of material lodging upon the strainer, and thereby assure that the strainer will present no interference to ready discharge of the contents of the digester, which is an important practical consideration.

Each section I6 and I6aof the strainer is provided, adjacent each end, at its mid-length and intermediate points with reinforcing ribs 2| conforming to walls I8 and I9 and disposed at the ,inner faces of these walls with respect to the linterior of the digester. A mounting strip 22, formed of metal resistant to the action of the acid liquor, is disposed in contact with back wall I1 of strainer section I6 and in alignment with center rib 2| of each of the sections of the strainer. Strip 22 is provided at each end with an openingwhich receives the reduced threaded stud 23 of a bolt 24 extending through lining b and provided with a shoulder 25 'at the outer end of stud 23, the latter receiving nut 23a and washer 23h. Bolt 24 is provided at its other end with a threaded stud 26 and a shoulder 21 at the inner end of the latter stud. Stud 26 projects through shell a of. the digester and receives upon its outer end a securing nut 28, washers 29 of suitable type being confined between this nut and shell a. A lead gasket 30 fits about stud 26 and is confined between shoulder 21 and the inner face of shell a and provides an effective uid-tight seal about' stud 26, when bolt 24 is forced toward shell a and secured thereto by means of the nut 28 and stud 26. Spacing washers 3| are disposed about stud 23 for properly spacing strip 22 with reference to the inner face .of lining b. Clamps 32 are disposed over the studs 23 of bolts 24 and are slotted at 33 for reception of. the terminal portions of rib 2|. Fingers 34 of the respective clamps 32, at each side of the slot 33 thereof, are bent at an angle to the body of the clamp so as to be inclined similarly to walls I8 and I9 of the strainer section I6. I'he clamps thus engage about the upper and lower portions of the strainer sections and cooperate with rib 2| to confine this section against lengthwise movement while accommodating transverse expansion and contraction thereof, it being noted that these clamps.

possess suicient resiliency for the latter purpose While being maintained in contact with the walls I8 and IS of the strainer section so as to prevent -any objectionable looseness or play of parts. Each strainer section is thus supported at its mid-length in such manner as to accommodate lengthwise expansion and contraction ofV the section while confining it against lengthwise movement, while also accommodating transverse expansion and contraction of the section, and the bolts 24 serve to support the weight of the strainer section from the steel shell a of the digester, to which shell the bolts are directly and tightly secured in the manner above described,l thus relieving the lining b of any load with respect to the strainer and associated parts.

The ends of the strainer sections are spaced apart a sufficient distance to accommodate' lengthwise expansion thereof, asshown at 35 in Figure 6, which is an inner face view of the adjacent end portions of two strainer sections I6 and the mounting means therefor. A bracket 36, conforming in shape to the adjacent ends of the sections I6, extends about the ends of these sections between the end ribs 2| thereof. This bracket is suitably secured, by welding or otherwise, to the end of one of the sections, spans the gap 35 between the section ends and extends an appreciable distance along the end of the other section, from which it is free. I'his bracket thus establishes a telescoping connection between the adjacent ends of the section effective vto exclude from the gap therebetween the contents of the digester while accommodating lengthwise expansion and contraction of the sections.

A fiat spacing bar 31 is disposed at the ends of these two adjacent sections of the strainer, at the outer face of the back walls thereof, and spans the gap between the ends of these walls. 'I'he inner face of spacing bar 31 is recessed at 38, as shown in Figure 3, to reduce the area of contact between this bar and back walls I1 ofthe strainer sections for reducing resistance to expansion and contraction of the latter. At each end bar 31 is provided with a boss 39 of rectangular shape. These bosses receive studs is conilned under pressure between shoulder 43y and the inner face of shell a, providinga uidtight seal above stud 44. The bolts 42 are thus secured directly to shell a so that the load of the parts 'carried by these bolts is supported byrthe shell, relieving the lining b of such load. Pte-l duced screw studs 41 extend inward from studs 40 of the bolts 42, and pass through clamps 43, the latter being confined between bosses 39'1Yand nuts 49 screwing onto studs 41. Eachclamp 48 is provided with a flange 50 which .engages..over` is prevented, and the load of such sections is supported directly bythe outer shelll of the digester'.

Each end of thestrainer structure .is closed byl a cup-shaped cap member -52a-suitably secured thereon, as by welding or otherwise, whichvcap members may be supported in the same manner as the brackets 36 are supported, so as to accommodate lengthwise and transverse expansion and contraction of the associated strainer sections.

Strainer section '16a is similar; :.to the other strainer sections except that.l it. is: provided with an outlet me'mber 53-depending from lower wall I9 and defining an outlet .opening therethrough,

v the upper wall 53a of member 53 constituting a continuation of upper wall I3 of' sections I6a, thesetwo walls being provided withacommon reinforcing rib 2|@ and member 53 preferably being provided, at its lower' end, with a, circumferential reinforcing flange 54. Member 53 receives the upper end portion of an elbow 55, conveniently formed of two sections -56 and 51 provided at their adjacent ends with circumferential bolting iianges 58 and 59, respectively, for- Section 51 of elbow4 55- is further provided,.adjacent its lower end. with a circumferential flange 60 secured bycap screws securing them together.

supporting means therefor, elbow 55, sleeve 63v and conduit 64, are formed of metal resistant to y the action of the acidvliquor. Conduit 64 serves tb conduct the withdrawn liquor to the circulating means previously referred to.

Sleeve 63 is provided, a short distance from its outer end, with a bolting flange 61 of considerably greater widththan flange 65. Flange 617 is provided with a thickened annular element 93 of la size to fit snugly within'the outer end of a nozzle 69 secured in a suitable .-manner, preferably by means of rivets 19, to shell a, at the outer face thereof. Flange 61 of sleeve 63 seats upon the outer-. face of a ange'll provided at the outer end of nozzle 69, these two flanges being secured tightlyv together in a suitable manner, conveniently by bolting.

Flange 62, at the inner end of sleeve 63, hasV an exterior diameter somewhat less -than-the interior diameter of nozzle 69 so that. ,in .assemblying sleeve 63 may be inserted through nozzle 69 from the outer end thereof and boltedto lthe nozzle by means of flange 61. Sleeve 63 extends through lining b of the digester, whenv mounted upon A the nozzle 69, and the lining extends about sleeve l63 and between the same and nozzle 69. The latter, like shell a, is of ordinarysteel and would be attacked by the acid liquor if the latter were brought into contact with these parts. portant, for the reasons previously setv forth, that this be.. avoided.' No great difliculty is encountered in forming fluid-tight. closures about such parts Ias pass through thelining, where these parts are readily accessible. ri'here may be dimculty, however, in eiecting a fluid-tight closure between the lining and the sleeve 63, particularly v at the portion of this sleeve which extends within the nozzle 69 and is there not readily accessible.

It 1S lm-a..

In order to guardagainst any possibility of leakage of acid liquor about the sleeve 63v into contact-with the nozzle 69,'we preferably provide means whereby a sealing compound, such as a suitab1ecement,` .may be flowed about sleeve 63, into such spaces-if any, as may exist between this sleeve` and the portion of the lining extending thereabout. With this object, we provide nozzle 69 with a suitable opening 12 extending radially of the neck of the nozzle. The portion of the lining. b extending into nozzle 69, about sleeve63 ,.,may` be provided with a passage 13 alignedz with opening 12 and extending therefrom to the exterior surface of sleeve '63. This passage may be provideddin yany suitable manner, and conveniently maybe formed by inserting through opening 12, into contact with the exterior surface of sleeve 63, any suitable instrument prior to placing 0L the portion of the lining which .extends into the nozzle.

With Such instrument in position, when the lining is placed inthe nozzle thepassage 13 will be formed in the placing -of the lining. After` the lining has been placed andis in finished condition, a suit-'able cement maybe delivered through opening 12 and passage 13, under appropriate pressure, thus providinga. sealing layer 14 extending about sleeve 63 between the lining surrounding this sleeve and, in some instances, between this portion of the ;,lining and'fiange 63 of sleeve 63. The passage 13 is, of course, iilled withand effectively sealed by the compound 14., In this manner possibility ofcontact of the acid liquor with the nozzle 69 and the shell a, due to leakage` about sleeve-63,

is eifectively eliminated. .Preferably the exterior surface of sleeve 63.is roughened at 15, to assure more intimate 'contact and a lcorrespondingly moreleifective sealibetween this surface and the cement ,or-compound 14. Surface 15 of the sleeve maybe roughenedby grinding,- sand blasting, or

- in any other appropriate manner.

In Figures 8 to 12, inclusive, we have illustrated a strainer and associated parts, embodying our invention, as applied to a dgester for useg in -a well. known digesting process employing an and the strainer and associated parts may beI formed of ordinary steel such as is employed in the shell and nozzle of the digester. The strainer 1B comprises a suitable number of sections 11 disposed with ends in alignment and opening one into the other, this strainer conforming in curvature to the interior of shell a and being disposed in close proximity to the inner face thereof,l it being noted that the shell has no lining since the alkali liquor does not attack the steel of which this shell is formed. Each of the sections 11 is provided, at its mid-length., with a reinforcing rib 18, which may be formed integral with' the upper and lower Walls 19 and 80, respectively, of the strainer section, these walls being perforated and connected by an imperforate back wall 8|, as before. A spacing bar '82 is securely welded at each end at 83, to shell a, and screw studs 84 are welded through 'the ends of this bar. Slotted clamps 85 are secured upon these studs, between nuts 88 and spacers 81, and receive the end portions of rib 18. In this manner, each section 11 is supported at its mid portion and is conned against lengthwise movement. Since spacing bar 82 is mounted upon shell a for expansion and contraction therewith, these parts being of similar metal, transverse expansion` and contraction of the strainer section are accommodated.

Theends of adjacent sections 16 of the strainer are spaced apart, as before, and this space is closed by a bracket 88 conforming in shape to the ends ,of the strainer section and provided with` a reinforcing rib 89. provided with terminal elements 90 conned between spacers 9| and nuts 92 threaded onto `the innerends of screw studs 93, the/latterV being welded in the ends of 'a spacing bar 94 welded at each end, at 95, to the inner face of shell a. The bracket 89 fits about the adjacent end portions of adjacent sections of the strainer but is not in tight contact therewith, slight clearance being provided suflicient to avoid interference with free lengthwise expansion and contraction of the strainer sections. AThe'strainer shown in Figure 9 extends more than the semi-circumference of the digester and, as previously noted, may be of any suitable extent up to the full circumference of the digester. The ends of this strainer may be closed in any suitable manner, if it extends less than the full interior circumference vofthe digester, conveniently by the same means as is provided for closing the ends of the strainer of Figure 1.

One of the strainer sections, designated 11a, is

provided through the back wall 8| a thereof with an outlet opening 96. A nozzle 91 is secured to shell a by rivets 98, the base flange of thisnozzle and the heads of the rivets being welded together and to shell a, as shown, to prevent possibility of leakage and assure adequate strength. A sleeve 99 is suitably secured to flange |00, at the outer end of nozzle 91, as by means oi' cap screws passing through flange |02 of the sleeve. At

Y its outer end sleeve 99 is provided with a ange |03 to which flange 66 of conduit is secured by cap screws |04. Sleeve 99 extends through nozzle 91 and through opening |05 in shell a, the inner end portion of this sleeve extending through opening 9G of back wall 8|a of screen section 11a, and being of slightly less exterior diameter than opening 96 to compensate for any slight differences in expansion and contraction of the slee've 99 and wall 8| a.

In both forms of our invention illustrated the construction of the strainer is, in general, sub- This bracket 88 is stantially the same except as to slight variations, particularly in the supporting means for the strainer, to accommodate the structure to the type of digester with which it is`i\used. In both forms the strainer and associated parts may be assembled and disassembled with expedition and facility, andl repair and replacement of parts may be effected with a minimum of delay and labor.

What we claim is:- f

1. In combination, a digester, and a substantially horizontal strainer supported within said digester in close proximity to the inner face thereof and conforming in-. contour thereto. said strainer being of triangular cross-section and having its upper surface iiat and inclined downward and inward of said digester, and its lower surface ilat andinclined downward and outward of said digester.

2. In combination, a digester, and a substantially horizontal strainer of triangular. cross-section supported within said digesterA in close proximity to the inner face thereof and conforming in contour thereto, the upper surface of said strainer being inclined downward and inward of said digesterl and the lower surface of said strainer being inclined downward and outward of said digester, the outer wall of saidstrainer being impe'rforate` and at least one of the other Walls thereof being perforated.

3. In combination, a digester, a strainer therein comprising separate sections disposed in endwise alignment and opening one into the other, means supporting the respective sections at the mid-length thereof While restraining them against lengthwise movement, and means excluding entry of the contents of said digester between adjacent ends of said sections While accommodating independent lengthwise expansion and contraction thereof.

4. In combination, a digester, a strainer therein comprising separate sections disposed in endwise alignment and opening one into the other, means supporting the respective sections at the mld-length thereof while restraining them against lengthwise movement, said supporting means accommodating transverse expansion and contraction of said sections, and means excluding entry of the vcontents of said digester between adjacent ends of said sections while accommodating independent lengthwise and transverse expansion and contraction thereof.

5. In combination, a digester comprising a metal outer wall and an acid resistant lining, a strainer therein comprising separate sections disposed in endwise alignment and opening one into the other, means supporting the respective sec` tions at the mid-length thereof while restraining them against lengthwise movement, said supporting means comprising bolts secured to said outer wall and extending through said lining, and

arate sections disposed in endwise alignment and g opening one into the other, each of the sections being provided at its mid-length with abutment l elements at its top and bottom, bolts secured t`o said wall, slotted clamps mounted on the inner ends of said bolts receiving said elements and engaging over the top and bottom portions of the respective sections, brackets engaging about the adjacent ends of said sections and eifecting closures therebetween while accommodating lengthwise expansion and contraction thereof, bolts secured to said wall, and clamps mounted on the inner ends of the latter bolts and extending about the top and the bottom portions of the brackets.

7. In combination, a digester comprising a metal wall, a strainer therein comprising separate sections disposed in endwise alignment and opening one into the other, each of the sections being provi-ded at its mid-length with la transverse reinforcing rib, bolts secured to said wall, slotted clamps mounted on the inner ends of said bolts receiving said rib and engaging over the top and bottom portions of the respective sections, brackets engaging about the adjacent ends of said sections and effecting closures therebetween while accommodating lengthwise expansion and contr-action thereof, bolts secured to said wall, and clamps mounted on the inner ends of the latter bolts and extending about the top and the bottom portions of said brackets.

8. In combination, a digester, a strainer therein comprising a section provided with a depending outlet member, means securing said section to said digester and supporting it therefrom, a nozzle secured to said digester exterior thereof, a sleeve secured to said nozzle and extending therethrough into said digester, and a'n elbow secured to the inner end of said sleeve and telescoping said outlet member, said elbow being free from said member whereby the latter and said elbow may expand and contract one independently of the other.

9. In combination, a digester comprising a metal outer wall and a lining therefor, a nozzle secured to the outer face of said outer wall,

a strainer within said digester provided with an outlet, a sleeve secured to said nozzle extending therethrough and through said lining and connected to said strainer outlet, said lining extending into said nozzle and about said sleeve, and a sealing compound about said sleeve between the latter and said lining and effective to prevent leakage about said sleeve to said nozzle of the liquid contents of said digester.

10. In combination, a digester comprising a metal outer wall and a lining therefor, a nozzle secure-d to the outer face of said outer wall, a strainer within said digester provided with an outlet, a sleeve secured to said nozzle extending therethrough and through said lining and connected to said strainer outlet, the outer surface of said sleeve being roughened, said lining extending into said nozzle and about said sleeve, and a sealing compound about said sleeve between the latter and said lining and effective to prevent leakage about said sleeve to said nozzle of the liquid contents of said digester.

1l. In combination, a digester comprising a metal outer wall and a lining therefor, a nozzle secured to the outer face of said outer wall, a strainer within said digester provided with an outlet, a sleeve secured to said nozzle extending therethrough an-d through said lining and connected to said strainer outletysaid lining extending into said nozzle and about said sleeve,

said nozzle having an opening therein and said lining being provided with a passage from said opening to the exterior of said sleeve, and a sealing compound forced through said opening and passage and between sai-d lining and said sleeve and nozzle and effective to prevent access to said nozzle of the liquid contents of said digester.

HERBERT W. GUETTLER. CLARENCE J. CHRISTIANSEN. 

